The present invention relates to a device for controlling a clutch for motor vehicles.
As is known, during the activation for opening and closure of the clutch, for example during the manoeuvres of change of gear and pick-up of the vehicle, the torque values transmitted by the engine to the drive wheels via the clutch itself depend mainly on the load which is applied to the clutch disc, the value of which depends on the position of the control lever of the clutch itself.
The operations of activation of the clutch are normally carried out manually by the driver of the vehicle, who regulates the position of the control lever, in order to obtain substantially gradual transfer of the torque via the clutch itself, and thus comfortable travel of the vehicle.
It is also known to carry out the operations of activation of the clutch fully automatically, by means of electronic control devices, the purpose of which, during activation of the clutch, is to regulate the position of the control lever of the clutch itself, according to a plurality of input signals.
The control devices of a known type are normally provided with an electronic system, which receives information signals at its input, and controls opening/closure of the clutch, by means of a solenoid valve, which receives pressurised fluid from a hydraulic circuit, and, on the basis of signals received, can activate an actuator which is connected to the clutch.
The control devices additionally comprise a position sensor, which is connected to the actuator, and generate as output a reaction signal which is correlated to the operative position of the actuator, and a control circuit which is disposed in the electronic system, and receives the reaction signal, on the basis of which a control signal is supplied to the solenoid valve.
In particular, the control circuit comprises a estimator circuit, which receives as input a plurality of information signals (i.e. values such as the position of the pedal of the accelerator, the angular speed of the engine, the angular speed of the clutch, the position of the brake pedal etc.), and supplies as output a signal for the estimated position of the clutch.
The control circuit additionally comprises an adder circuit, which receives as input the reaction signal of the position sensor and the signal for the estimated position, and supplies an error signal to an input of a controller circuit (for example of the proportional-integral-derivative PID type), which in turn supplies as output the control signal of the solenoid valve.
The control devices of the known type have the disadvantage that if a fault of the position sensor occurs, the control circuit receives a reaction signal which has an incorrect value, and consequently it is no longer able to supply a correct control signal to the solenoid valve.
In these conditions, activation of the actuator becomes inaccurate, problematic and/or impossible, with obvious safety risks, caused by the lack of opening/closure of the clutch.
The object of the present invention is to provide a control device for a clutch for motor vehicles, which can control the actuator unit of the clutch, even if the aforementioned position sensor is faulty.